Buttons is a good idea, especially if Grump don't like it init.....
As for sealer, have you tried Coats of CA on them and polish to a shine then resin cast them? I have seen it done that way before.
Also seen the tubes painted white, cast in a resin, turned down to 50% of finished size then fit the transfers and then cast again to enable them to be turned down to the right size. Quite good effect.